U.S. patent number 8,755,312 [Application Number 13/092,335] was granted by the patent office on 2014-06-17 for apparatus and method for supporting gateway node reselection in communication system.
This patent grant is currently assigned to Samsung Electronics Co., Ltd.. The grantee listed for this patent is Huarui Liang, Hong Wang, Lixiang Xu. Invention is credited to Huarui Liang, Hong Wang, Lixiang Xu.
United States Patent |
8,755,312 |
Liang , et al. |
June 17, 2014 |
Apparatus and method for supporting gateway node reselection in
communication system
Abstract
An apparatus and a method for supporting gateway node
reselection in a communication system during a process in which a
UE hands over from a source base station to a destination base
station are provided. The apparatus includes the source base
station for providing the destination base station with information
for access control determination, the destination base station for
making an access control determination according to the information
provided by the source base station, the UE or a network for
initiating a gateway reselection process according to the result of
the access control determination. With the method, the reselection
of Packet Data Network Gateway (PDN GW) or GGSN is implemented in a
simple and reliable way by optimizing the existing signaling
processes, in the case of user plane node reselection because UE
changes position or handover to another base station.
Inventors: |
Liang; Huarui (Beijing,
CN), Wang; Hong (Beijing, CN), Xu;
Lixiang (Beijing, CN) |
Applicant: |
Name |
City |
State |
Country |
Type |
Liang; Huarui
Wang; Hong
Xu; Lixiang |
Beijing
Beijing
Beijing |
N/A
N/A
N/A |
CN
CN
CN |
|
|
Assignee: |
Samsung Electronics Co., Ltd.
(Suwon-si, KR)
|
Family
ID: |
44858216 |
Appl.
No.: |
13/092,335 |
Filed: |
April 22, 2011 |
Prior Publication Data
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|
|
Document
Identifier |
Publication Date |
|
US 20110268086 A1 |
Nov 3, 2011 |
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Foreign Application Priority Data
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Apr 30, 2010 [CN] |
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2010 1 0162474 |
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Current U.S.
Class: |
370/310 |
Current CPC
Class: |
H04W
36/0079 (20180801); H04W 36/0058 (20180801); H04W
36/12 (20130101) |
Current International
Class: |
H04B
7/00 (20060101) |
Field of
Search: |
;370/310,328,329,331,431
;709/223,238,249 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
3GPP 23.829 V1.0.1 (Mar. 2010), LOcal IP Access and Selected IP
Traffic Offload, 3GPP, Mar. 2010, pp. 1-37. cited by examiner .
3GPP TS 23.401 V9.4.0 (Mar. 2010), GPRS enhancements for E-UTRAN
access, 3GPP, Mar. 2010, pp. 1-140. cited by examiner .
3GPP TS 23.401 V9.4.0 (Mar. 2010), GPRS enhancements for E-UTRAN
access, 3GPP, Mar. 2010, pp. 141-258. cited by examiner.
|
Primary Examiner: Levitan; Dmitry H
Attorney, Agent or Firm: Jefferson IP Law, LLP
Claims
What is claimed is:
1. A method for supporting gateway node selection during a process
in which a User Equipment (UE) hands over from a source base
station to a target base station, the method comprising: providing,
in a handover request message sent by the source base station, the
target base station with information required for a determination
of whether to grant the UE access to the target base station;
determining, by the target base station, access control according
to the information provided by the source base station; and
initiating, by the UE or a network, a gateway selection process for
the UE when the result of the access control determination
indicates that handover preparation has failed.
2. The method according to claim 1, wherein the information for the
access control determination provided by the source base station
includes information of a user plane gateway, and wherein the
information of the user plane gateway node comprises at least one
of an IP address and an identifier of a Packet Data Network Gateway
(PDN GW).
3. The method according to claim 1, wherein the determining of the
access control comprises when determining, by the target base
station, that the handover fails, sending, by the target base
station, a handover preparation failure message to the source base
station.
4. The method according to claim 3, wherein the initiating of the
gateway reselection process comprises: upon receiving the handover
preparation failure message, requesting, by the source base
station, a core network node to initiate a PDN connection releasing
process; after the completion of the PDN connection releasing
process, initiating, by the UE, a PDN connection establishment
request to a Mobile Management Entity (MME); and upon receiving the
PDN connection establishment request, reselecting, by the MME, a
PDN GW for the UE according to subscription information of the UE
and information of a currently accessed base station.
5. The method according to claim 4, wherein the requesting of the
core network node to initiate a PDN connection releasing process
comprises: according to the received handover preparation failure
message, sending, by the source base station, a request message to
the MME requesting the MME to trigger the PDN connection releasing
process; and sending, by the MME, a PDN connection releasing
request message to the UE.
6. The method according to claim 4, wherein the requesting of the
core network node to initiate a PDN connection releasing process
comprises: upon receiving the handover preparation failure message,
sending, by the source base station, a Radio Resource Connection
(RRC) releasing message to the UE; and upon receiving the RRC
releasing message, instructing, by the UE, a Non-Access Stratum
(NAS) layer to initiate the PDN connection releasing process.
7. The method according to claim 6, wherein the initiating of the
PDN connection establishment request to the MME comprises: after
the completion of the PDN connection releasing process, initiating,
by the UE, a PDN connection establishment request to the MME as
required by a service, or, after the completion of the PDN
connection releasing process, initiating, by the UE, a PDN
connection establishment request to the MME.
8. A system for supporting gateway node selection during a process
in which a User Equipment (UE) hands over from a source base
station to a target base station, the system comprising: a source
base station for providing, in a handover request message, the
target base station with information required for a determination
of whether to grant the UE access to the target base station; a
target base station for making an access control determination
according to the information provided by the source base station;
and a UE or a network for initiating a gateway selection process
for the UE when the result of the access control determination
indicates that handover preparation has failed.
9. The system according to claim 8, wherein the information for the
access control determination provided by the source base station
includes information of a user plane gateway, and wherein the
information of the user plane gateway node comprises at least one
of an IP address and an identifier of a Packet Data Network Gateway
(PDN GW).
10. The system according to claim 8, wherein, when the target base
station determines that the handover has failed, the target base
station sends a handover preparation failure message to the source
base station.
11. The system according to claim 10, further comprising: a Mobile
Management Entity (MME) for, upon receiving the PDN connection
establishment request, reselecting a PDN GW for the UE according to
subscription information of the UE and information of a currently
accessed base station, wherein the source base station, upon
receiving the handover preparation failure message, requests a core
network node to initiate a PDN connection releasing process, and
wherein the UE, after the completion of the PDN connection
releasing process, initiates a PDN connection establishment request
to an MME.
12. The system according to claim 11, wherein the source base
station, according to the received handover preparation failure
message, sends to the MME a request message requesting the MME to
trigger the PDN connection releasing process, and wherein the MME
sends a PDN connection releasing request message to the UE.
13. The system according to claim 11, wherein the source base
station, upon receiving the handover preparation failure message,
sends a Radio Resource Connection (RRC) releasing message to the
UE, and wherein the UE, upon receiving the RRC releasing message,
instructs a Non-Access Stratum (NAS) layer to initiate the PDN
connection releasing process.
14. The system according to claim 13, wherein the UE, after the
completion of the PDN connection releasing process, initiates a PDN
connection establishment request to the MME as required by a
service, or, after the completion of the PDN connection releasing
process, the UE initiates a PDN connection establishment request to
the MME.
Description
PRIORITY
This application claims the benefit under 35 U.S.C. .sctn.119(a) of
a Chinese patent application filed on Apr. 30, 2010 in the Chinese
Intellectual Property Office and assigned Serial No.
201010162474.8, the entire disclosure of which is hereby
incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of mobile communication
technologies. More particularly, the present invention relates to
an apparatus and a method for supporting gateway node reselection
in a communication system.
2. Description of the Related Art
FIG. 1 is a schematic diagram illustrating the structure of a Long
Term Evolution (LTE) system in the prior art.
Referring to FIG. 1, a System Architecture Evolution (SAE) includes
a User Equipment (UE) 101 which is a terminal device for receiving
data. An Evolved-Universal Terrestrial Radio Access Network
(E-UTRAN) 102 is a radio access network, which includes a macro
base station (e.g., an evolved Node B (eNB)) providing the UE with
an access radio network interface. A Mobile Management Entity (MME)
103 is responsible for managing mobile context, session context,
and security information for the UE. A Service Gateway (SGW) 104
mainly provides the function of the user plane. In practical
networks, the MME 103 and the SGW 104 may be located at the same
physical entity. A Packet Data Network Gateway (PDN GW) 105 is
responsible for the functions of charging, legal listening, and so
on, which may be located at the same physical entity as the SGW
104. A Policy and Charging Rule Function (PCRF) 106 provides
Quality of Service (QoS) policies and charging rules. A General
Packet Radio Service Supporting Node (SGSN) 108 is a network node
device providing routes for data transmission in a Universal Mobile
Telecommunication System (UMTS). A Home Subscriber Server (HSS) 109
is a home subsystem of the UE, responsible for saving subscriber
information including the current location of the UE, the address
of the serving node, subscriber security information, packet data
context of the UE, and so on.
With the increase in UE service data rate, operators provide a new
technology of Selected IP Traffic Offload (SIPTO), in which in the
process of the movement of a UE that has accessed a certain
service, the network side can handover the UE automatically to a
near radio network access point, which reduces the costs invested
for the transmission network and provides a better experience for
the high data rate. The current 3.sup.rd Generation Partnership
Project (3GPP) standard has proposed that the network needs to
support the abilities of SIPTO and Local IP Access (LIPA). In
SIPTO, the UE accesses the Internet and other external networks
through a Home evolved Node B (HeNB), a Home Node B (HNB), or an
eNB. When the UE accesses the network, the network side selects a
suitable user plane node for the UE. In LIPA, on the other hand,
the UE accesses a home network and an intranet through an HeNB or
an HNB. In the implementation of LIPA, the network side also needs
to select a suitable user plane node for the UE. The user plane
node may be a user plane network device or a user plane gateway.
The suitable user plane node usually refers to a user plane network
device or a user plane gateway near to the UE. For an SAE system,
the user plane node is an SGW or a PDN GW. And for a UMTS system,
the user plane node is an SGSN or a Gateway General Packet Radio
Services (GPRS) Supporting Node (GGSN).
FIG. 2 is a schematic diagram illustrating an application scenario
in which a network reselects a user plane node for a UE in order to
allocate its resources in an optimized way in the prior art.
Referring to FIG. 2, when the UE changes position, when a UE
handover to another base station, or when the operator updates the
policies after the network has selected a suitable PDN GW or GGSN,
it becomes possible that the network reselects another PDN GW or
GGSN for the UE in order to allocate its resources in an optimized
way. The current standards have not specified how to implement the
process of reselection such that when the above situation occurs,
the UE can not continue enjoying the data service normally, which
impairs the user's experience.
SUMMARY OF THE INVENTION
Aspects of the present invention are to address at least the
above-mentioned problems and/or disadvantages and to provide at
least the advantages described below. Accordingly, an aspect of the
present invention is to provide an apparatus and a method for
supporting gateway node reselection, which is capable of
implementing reselection of a Packet Data Network Gateway (PDN GW)
or a Gateway General Packet Radio Services (GPRS) Supporting Node
(GGSN), in a communication system.
To attain the above aspects, the technical solutions of the present
invention may be implemented in the following way.
In accordance with an aspect of the present invention, a method for
supporting gateway node reselection during a process in which a
User Equipment (UE) hands over from a source base station to a
destination base station is provided. The method includes
providing, by a source base station, the destination base station
with information for access control determination, determining, by
the destination base station, access control according to the
information provided by the source base station, and initiating, by
the UE or a network, a gateway reselection process according to the
result of the access control determination.
The information for access control determination provided by the
source base station may include information of a user plane gateway
node near to the source base station, wherein the information of
the user plane gateway node is an IP address or identifier of a PDN
GW.
The information for access control determination may be contained
in a handover request message sent from the source base station to
the destination base station.
When determining that successful handover can not be ensured, the
destination base station may determine that the handover fails and
send a handover preparation failure message to the source base
station.
The initiating of a gateway reselection process according to the
result of the access control determination by the UE or the network
may includes, upon receiving the handover preparation failure
message, requesting, by the source base station, a core network
node to initiate a PDN connection releasing process, after the
completion of the PDN connection releasing process, initiating, by
the UE, a PDN connection establishment request to a Mobile
Management Entity (MME), and, upon receiving the PDN connection
establishment request, reselecting, by the MME, a PDN GW for the UE
according to subscription information of the UE and information of
a currently accessed base station.
The method of requesting, by the source base station, a core
network node to initiate a PDN connection releasing process upon
receiving the handover preparation failure message may include
sending, by the source base station, a request message to the MME
requesting the MME to trigger the PDN connection releasing process
according to the received handover preparation failure message, and
sending, by the MME, a PDN connection releasing request message to
the UE.
The method of requesting, by the source base station, a core
network node to initiate a PDN connection releasing process upon
receiving the handover preparation failure message may include upon
receiving the handover preparation failure message, sending, by the
source base station, a Radio Resource Connection (RRC) releasing
message to the UE, and, upon receiving the RRC releasing message,
instructing, by the UE, a Non-Access Stratum (NAS) layer to
initiate the PDN connection releasing process.
The process of initiating, by the UE, a PDN connection
establishment request to the MME after the completion of the PDN
connection releasing process may include after the completion of
the PDN connection releasing process, initiating, by the UE, a PDN
connection establishment request to the MME as required by the
service, or, after the completion of the PDN connection releasing
process, initiating, by the UE, a PDN connection establishment
request to the MME immediately.
In accordance with an aspect of the present invention, a method for
supporting gateway node reselection is provided. The method
includes initiating, by a Policy and Charging Rule Function (PCRF),
an IP Connectivity Access Network (CAN) session modification
process with new policy information carried therein to a PDN GW,
sending, by the PDN GW, at least one of a bearer update request
message and a newly-defined General Packet Radio Services (GPRS)
Tunneling Protocol (GTP) message to a Serving Gateway (SGW) in
response to the modification process, the bearer update request
message or the newly-defined GTP message having the new policy
information carried therein, forwarding, by the SGW, the bearer
update request message or the newly-defined GTP message to an MME,
and determining, by the MME, according to the new policy
information, whether the MME needs to trigger a PDN GW reselection
process, and if yes, reselecting a PDN GW for UE.
The method of determining, by the MME, according to the new policy
information, whether the MME needs to trigger a PDN GW reselection
process, and if yes, reselecting a PDN GW for UE may include
determining, by the MME, according to the new policy information,
whether it needs to trigger a PDN connection deactivation process,
and if yes, sending a PDN connection deactivation request message
to the UE, upon receiving the deactivation request message,
reinitiating, by the UE, a PDN connection request with instruction
information requesting PDN GW reselection carried therein, and
reselecting, by the MME, a PDN GW for the UE according to the
instruction information.
The method may further include sending, by the MME, updated
subscription information to an HSS to update subscription
information of the UE, including LIPA information corresponding to
the Access Point Name (APN), which step is performed in a bearer
modification process or the PDN GW reselection process triggered by
the MME, returning, by the HSS, an update confirmation message to
the MME after update the subscription information of the UE, and
updating, by the MME, the stored subscription information of the
UE.
As can be seen from the description, with the methods for
supporting gateway node reselection according to exemplary
embodiments of the present invention, the reselection of PDN GW or
GGSN can be implemented in a simple and reliable way by optimizing
the existing signaling processes, in the case of user plane node
reselection because UE changes position or handover to another base
station.
Other aspects, advantages, and salient features of the invention
will become apparent to those skilled in the art from the following
detailed description, which, taken in conjunction with the annexed
drawings, discloses exemplary embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other aspects, features, and advantages of certain
exemplary embodiments of the present invention will be more
apparent from the following description taken in conjunction with
the accompanying drawings, in which:
FIG. 1 is a schematic diagram illustrating the structure of a Long
Term Evolution (LTE) system in the prior art;
FIG. 2 is a schematic diagram illustrating an application scenario
in which the network reselects a user plane node for a User
Equipment (UE) in order to allocate its resources in an optimized
way in the prior art;
FIG. 3 is a schematic flowchart illustrating a method for
supporting gateway node reselection in a communication system
according to an exemplary embodiment of the present invention;
FIG. 4 is a schematic flowchart illustrating a method for
supporting gateway node reselection in a communication system
according to an exemplary embodiment of the present invention;
FIG. 5 is a schematic flowchart illustrating an implementation of a
method for supporting gateway node reselection in a communication
system according to an exemplary embodiment of the present
invention;
FIG. 6 is a schematic flowchart illustrating an implementation of a
method for supporting gateway node reselection in a communication
system according to an exemplary embodiment of the present
invention;
FIG. 7 is a schematic diagram illustrating an implementation for
supporting gateway node reselection when there are multiple Packet
Data Network (PDN) connections or bearers for a UE in a
communication system, according to an exemplary embodiment of the
present invention;
FIG. 8 is a schematic diagram illustrating an implementation for
supporting gateway node reselection when there are multiple PDN
connections or bearers for a UE in the case of S1 Handover (HO) in
a communication system, according to an exemplary embodiment of the
present invention;
FIG. 9 is a block diagram of a base station in a communication
system according to an exemplary embodiment of the present
invention; and
FIG. 10 is a block diagram of a Mobile Management Entity (MME) in a
communication system according to an exemplary embodiment of the
present invention.
Throughout the drawings, it should be noted that like reference
numbers are used to depict the same or similar elements, features,
and structures.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
The following description with reference to the accompanying
drawings is provided to assist in a comprehensive understanding of
exemplary embodiments of the invention as defined by the claims and
their equivalents. It includes various specific details to assist
in that understanding but these are to be regarded as merely
exemplary. Accordingly, those of ordinary skill in the art will
recognize that various changes and modifications of the embodiments
described herein can be made without departing from the scope and
spirit of the invention. In addition, descriptions of well-known
functions and constructions may be omitted for clarity and
conciseness.
The terms and words used in the following description and claims
are not limited to the bibliographical meanings, but, are merely
used by the inventor to enable a clear and consistent understanding
of the invention. Accordingly, it should be apparent to those
skilled in the art that the following description of exemplary
embodiments of the present invention is provided for illustration
purpose only and not for the purpose of limiting the invention as
defined by the appended claims and their equivalents.
It is to be understood that the singular forms "a," "an," and "the"
include plural referents unless the context clearly dictates
otherwise. Thus, for example, reference to "a component surface"
includes reference to one or more of such surfaces.
As described in the BACKGROUND OF THE INVENTION section, a network
may reselect another Packet Data Network Gateway (PDN GW) or
Gateway General Packet Radio Services (GPRS) Supporting Node (GGSN)
for User Equipment (UE) in order to allocate its resources in an
optimized way in a communication system, in the case that:
1) the UE changes position or handover to another base station;
or
2) the operator updates the policies.
Exemplary methods for supporting gateway node reselection will be
described in more detail with reference to the above two cases.
FIG. 3 is a schematic flowchart illustrating a method for
supporting gateway node reselection in a communication system
according to an exemplary embodiment of the present invention. In
FIG. 3, a method for supporting gateway node reselection, applied
to user plane node reselection because the operator updates the
policies, is illustrated
Referring to FIG. 3, the method includes:
Step 301: a Policy and Charging Rule Function (PCRF) 330 initiates
an IP Connectivity Access Network (CAN) session modification
process with new policy information carried therein to a PDN GW
320;
Step 302: the PDN GW 320 sends a bearer update request message or a
newly-defined General Packet Radio Services (GPRS) Tunneling
Protocol (GTP) message to an Service Gateway (SGW) 310 in response
to the modification process, the bearer update request message or
the newly-defined GTP message having the new policy information
carried therein;
Step 303: the SGW 310 forwards the bearer update request message or
the newly-defined GTP message to a Mobile Management Entity (MME)
300;
Step 304: the MME 300 determines, according to the new policy
information, whether it needs to trigger a PDN GW reselection
process, and if yes, reselects another PDN GW 320 for UE.
In an exemplary implementation, step 304 may include:
Step 304-1: the MME 300 determines, according to the new policy
information, whether it needs to trigger a PDN connection
deactivation process, and if yes, sends a PDN connection
deactivation request message to the UE;
Step 304-2: upon receiving the deactivation request message, the UE
reinitiates a PDN connection request with instruction information
requesting PDN GW reselection carried therein;
Step 304-3: the MME 300 reselects a PDN GW 320 for the UE according
to the instruction information.
Further, the method may include the following steps:
Step 305: the MME 300 sends updated subscription information to a
Home Subscriber Server (HSS) 340 to update subscription information
of the UE, including Local IP Access (LIPA) information
corresponding to the Access Point Name (APN). For example, the LIPA
information corresponding to the APN indicates that it does not
need to implement LIPA. The purpose of this is so that a next or
subsequent time when the MME 300 receives a PDN connection request
or another Non-Access Stratum (NAS) request message from the UE,
the MME 300 selects, according to the LIPA information
corresponding to the APN, another PDN GW 320, rather than selecting
repeatedly the PDN GW 320 before the policy modification.
Step 305 may be performed in a bearer modification process or the
PDN GW reselection process triggered by the MME 300 (i.e. the PDN
connection deactivation process triggered by the MME 300). This
step is optional. That is, if the MME 300 does not perform step
305, the MME 300 determines, when implementing the selection of PDN
GW next time, the selection of PDN GW according to the updated
policy information and the LIPA information corresponding to the
APN collectively.
Step 306: after step 305 is performed, the HSS 340 returns an
update confirmation message to the MME 300 after updating the
subscription information of the UE successfully, and the MME 300
also updates the stored subscription information of the UE.
As can be seen, with the above exemplary method, when the operator
updates the policy information, the PDN GW 320 sends a policy
update notice to the SGW 310, which forwards the policy update
notice to the MME 300, and the MME 300 becomes aware that the
relevant policies have been changed, such that the MME 300 can
determine, according to the new policy information, whether it
needs to implement user plane node reselection and accomplish the
reselection process. For example, although the MME 300 has
originally determined that it needs to select a PDN GW nearer to a
certain base station for the UE, according to the Selected IP
Traffic Offload (SIPTO) identifier in the subscription information
of the UE, when receiving the changed policy information through
step 303, the MME 300 determines that it does not any longer need
to select the nearer PDN GW for the UE, according to the new policy
information, even if the subscription information of the UE
contains the SIPTO identification information. The MME 300 may also
choose to inform HSS, so that when the UE accesses the network
again or again requests a PDN connection, the MME 300 may select a
corresponding PDN GW for the UE directly according to the updated
subscription information.
FIG. 4 is a schematic flowchart illustrating a method for
supporting gateway node reselection in a communication system
according to an exemplary embodiment of the present invention. In
FIG. 4, a method for supporting gateway node reselection, applied
to user plane node reselection because a UE changes position or
hands over to another base station, is illustrated.
Referring to FIG. 4, the method includes:
Step 401: a source base station provides a destination base station
(target base station) with information for access control
determination;
Step 402: the destination base station makes an access control
determination according to the information provided by the source
base station;
Step 403: the UE or the network initiates a gateway reselection
process according to the result of the access control
determination.
Steps 401-403 will be described in more detail below with reference
to specific implementations.
FIG. 5 is a schematic flowchart illustrating an implementation of a
method for supporting gateway node reselection in a communication
system according to an exemplary embodiment of the present
invention
Referring to FIG. 5, an exemplary implementation includes the
following steps.
Step 501: a handover measurement process is performed by a UE 500
and a source base station 510.
Step 502: the source base station 510 implements the handover
according to a measurement report sent from the UE 500.
Step 503: the source base station 510 sends a handover request
message to a destination base station 520, the handover request
message containing the information for the access control
determination by the destination base station 520, e.g. information
of a PDN GW 550 near to the source base station 510, which may be
an IP address or identifier of the PDN GW 550 near to the source
base station 510, or information of an SGW 540.
Step 504: the destination base station 520 determines whether the
handover can be continued, and if not, performs step 505;
otherwise, the destination base station 520 implements the handover
process according to a prior art solution, the details of which
will not be described here.
Step 505: the destination base station 520 sends a handover
preparation failure message to the source base station 510.
There are two exemplary methods of the procedure after step 505,
depending on different handover preparation failure messages.
First, the source base station 510 cuts the radio connection of the
UE 500 upon receiving the handover preparation failure message and
afterwards, reinitiates a PDN connection establishment request to
an MME 530 when the UE 500 requests a service. The flow thereof is
the same as in the prior art and will not be detailed here.
Second, the handover preparation failure message sent in step 505
further contains information indicating the reason for the handover
failure and step 506 is performed successively.
Step 506: the source base station 510 sends a request message
requesting the MME 530 to trigger a PDN connection releasing
process, according to the information indicating the reason for the
handover failure contained in the received handover preparation
failure message, the message being an S1-AP message.
Step 507: the MME 530 sends the PDN connection releasing request
message to the UE 500.
Step 508: the UE 500 initiates a PDN connection establishment
request to the MME 530 as required by the service, and, upon
receiving the PDN connection establishment request, the MME 530
reselects a PDN GW 550 for the UE 500 according to subscription
information of the UE 500 and information of a currently accessed
base station.
In an exemplary implementation, the PDN connection releasing
request message sent from the MME 530 to the UE 500 may further
include instruction information requesting the UE 500 to initiate a
PDN connection establishment request immediately. Accordingly, step
508 becomes initiating, by the UE 500, a PDN connection
establishment request to the MME 530 immediately, and, upon
receiving the PDN connection establishment request, reselecting, by
the MME 530, a PDN GW 550 for the UE 500 according to subscription
information of the UE 500 and information of a currently accessed
base station.
FIG. 6 is a schematic flowchart illustrating an implementation of a
method for supporting gateway node reselection in a communication
system according to an exemplary embodiment of the present
invention.
Alternatively, the flow of the other method for supporting gateway
node reselection may be that shown in FIG. 6.
Referring to FIG. 6, steps 601-605 are the same as steps 501-505
and therefore their description as well as the description of each
component 600-650, will not be provided again for sake of
convenience.
Step 606: a source base station 610 sends a Radio Resource
Connection (RRC) releasing message to a UE 600.
Step 607: upon receiving the RRC releasing message, the UE 600
instructs the NAS layer to initiate a PDN connection releasing
process.
Step 608: after the completion of the PDN connection releasing
process, the UE 600 initiates a PDN connection establishment
request to an MME 630 as required by the service; or after the
completion of the PDN connection releasing process, the UE 600
initiates a PDN connection establishment request to the MME 630
immediately.
Although not shown in FIG. 6, upon receiving the PDN connection
establishment request, the MME 630 reselects a PDN GW 650 for the
UE 600 according to subscription information of the UE 600 and
information of a currently accessed base station.
In an exemplary implementation, the RRC releasing message in step
606 further contains information indicating the reason for the
handover failure. Accordingly in step 607, the UE 600 receives the
RRC releasing message and instructs the NAS layer to initiate a PDN
connection releasing process according to the indicative
information contained therein, and step 608 is performed
afterwards.
When there are multiple PDN connections or bearers for UE, a
situation may occur in which some bearers or the bearers on some
PDN connections are switched successfully and some bearers are
switched unsuccessfully. A corresponding implementation, as shown
in FIG. 7.
FIG. 7 is a schematic diagram illustrating an implementation for
supporting gateway node reselection when there are multiple Packet
Data Network (PDN) connections or bearers for a UE in a
communication system, according to an exemplary embodiment of the
present invention.
Referring to FIG. 7, steps 701-704 are the same as steps 501-504 in
the above exemplary embodiment and therefore their description, as
well as the description of each component 700-750, will not be
provided again for sake of convenience.
Step 705: a destination base station 720 determines, according to
the information for access control determination, that some PDN
connections can not be switched successfully to the destination
network. For example, if, according to the information of the user
plane node, i.e. a PDN connection is based on LIPA or SIPTO, the
destination base station 720 determines that the PDN connection can
not continue keeping the service continuity in the destination
network, then the destination base station 720 determines that the
PDN connection should be put into a list of unsuccessful bearers.
In the handover request confirmation message, the bearer
information included in the PDN connection based on LIPA or SIPTO
is put into a list of unsuccessful bearer information for notifying
to a source base station 710.
Step 706: the destination base station 720 sends a path transfer
request to an MME 730, the request message including unsuccessful
bearer information, including bearer information included in the
PDN connection based on LIPA. The MME 730 initiates a special
bearer deactivation process or PDN connection deactivation process
according to the information.
The deactivation message initiated by the MME 730 contains an
indication requesting the UE 700 to initiate a PDN connection
request process. The UE 700 initiates a PDN connection
establishment request to the MME 730 according to the indication.
The MME 730 reselects another PDN GW 750 for the UE 700 according
to the subscription information of the UE 700, e.g. APN information
and so on. Alternatively, after the deactivation process is
initiated by the MME 730, the UE 700 initiates a PDN connection
establishment process just when the UE 700 requests the service as
required by the service.
Alternatively, in the case of S1 HO, when there are multiple PDN
connections or bearers for UE, a situation may also occur in which
some bearers or the bearers on some PDN connections are switched
successfully and some bearers are switched unsuccessfully.
FIG. 8 is a schematic diagram illustrating an implementation for
supporting gateway node reselection when there are multiple PDN
connections or bearers for a UE in the case of S1 Handover (HO) in
a communication system, according to an exemplary embodiment of the
present invention.
Referring to FIG. 8, a corresponding implementation includes the
following steps.
Step 801: the source base station 810 sends a handover request
message to the MME 830.
The MME 830 makes an access control determination according to ID
information or location region information of the destination base
station 820 contained in the message, and the information for
access control determination requested from the destination base
station 820, e.g. information of a PDN GW 850 near to the
destination base station 820; or information of the user plane near
to the destination base station 820 obtained through a node such as
Operation And Management (OAM) or information of the user plane
near to the destination base station 820 stored in advance.
If the bearer of a PDN connection related to LIPA or SIPTO can not
ensure the service continuity, the handover request message in step
802 has only a list of successful bearers carried therein, and does
not include unsuccessful bearer information related to LIPA or
SIPTO. Alternatively, the handover request message in step 802 has
successful bearer information and unsuccessful bearer information
carried therein.
Step 803: the destination base station 820 sends a handover request
confirmation message to the MME 830.
Step 804: the MME 830 initiates a special bearer deactivation
process or PDN connection deactivation process according to the
unsuccessful bearer information. There is no strict sequence
relationship in time between this step and steps 802 or 803.
The MME 830 initiates a deactivation message to the UE 800. The UE
800 initiates a PDN connection establishment process to the MME 830
immediately according to the indication contained in the
deactivation message, and the MME 830 reselects a PDN GW 850 for
the UE 800. Alternatively, the UE 800 initiates a PDN connection
establishment process as required by the service, and the MME 830
reselects a PDN GW 850 for the UE 800.
It should be noted that in the above exemplary embodiments, the way
in which the destination base station or the core network node,
e.g. the MME, obtains the information for access control is not
limited to handover signaling, but it may make an access control
determination through an OAM server or information pre-stored
before the handover. Also, the base station (including the source
base station and the destination base station) mentioned in the
various embodiments may be a Home evolved Node B (HeNB) or eNB. In
addition, although the above embodiments are all described with a
System Architecture Evolution (SAE) system as an example, the
methods provide by the present invention also apply to a Universal
Mobile Telecommunication System (UMTS) system, where the base
station is a Home Node B (HNB) or Node B, the MME corresponds to an
General Packet Radio Service Supporting Node (SGSN) in the UMTS
system, and the PDN GW corresponds to a GGSN in the UMTS system.
Moreover, the various handover scenarios to which the methods
provided by the above embodiments apply, are not limited to S1
handover, X2 handover, or the handover within the UMTS network.
FIG. 9 is a block diagram of a base station in a communication
system according to an exemplary embodiment of the present
invention. The base station described in FIG. 9 may include a
source base station and a destination base station.
Referring to FIG. 9, the base station includes a Radio Frequency
(RF) processor 910, a modem 920, a backhaul communication unit 930,
a storage unit 940, and a controller 950.
The RF processor 910 performs functions, such as signal band
conversion and amplification, to transmit and receive signals over
a radio channel. That is, the RF processor 910 up-converts a
baseband signal output from the modem 920 into an RF signal and
transmits the RF signal over an antenna. Also, the RF processor 910
down-converts the RF signal received over the antenna into the
baseband signal. Although not illustrated, for example, the RF
processor 910 may include an amplifier, a mixer, an oscillator, a
Digital to Analog Converter (DAC), an Analog to Digital Converter
(ADC) and the like.
The modem 920 converts the baseband signal and a bit string
according to a physical layer standard of the system. For example,
to transmit data, the modem 920 generates complex symbols by
encoding and modulating a transmit bit string, maps the complex
symbols to subcarriers, and constitutes Orthogonal
Frequency-Division Multiplexing (OFDM) symbols by applying Inverse
Fast Fourier Transform (IFFT) and inserting a Cyclic Prefix (CP).
When receiving data, the modem 920 splits the baseband signal
output from the RF processor 910 into OFDM symbols, restores the
signals mapped to the subcarriers using Fast Fourier Transform
(FFT), and restores the receive bit string by demodulating and
decoding the signals.
The backhaul communication unit 930 provides an interface for the
base station to communicate with other entities (i.e., other BSs,
an MME, and the like). More specifically, the backhaul
communication unit 930 converts the bit string transmitted by the
base station into a physical signal, and converts the physical
signal received at the base station into the bit string.
The storage unit 940 stores program codes and system information
required for the operations of the BS. The storage unit 940
provides stored data to the controller 950 upon a request from the
controller 950.
The controller 950 controls the functions of the BS. For example,
the controller 950 generates a transmit packet and a message and
provides the modem 920 with the transmit packet and the message.
The controller 950 also processes a receive packet and a message
from the modem 920. More particularly, according to an exemplary
embodiment of the present invention, the controller 950 controls a
function for supporting gateway node reselection, such as during
the process that a UE hands over from a source base station to a
destination base station.
For example, the controller 950 controls a function for supporting
gateway node reselection, such as during the process that a UE
hands over from a source base station to a destination base station
as illustrated in FIG. 4 to FIG. 8. More particularly, the
controller 950 of a source base station provides a destination base
station via the backhaul communication unit 930 with information
for access control determination. The controller 950 of the
destination base station makes an access control determination
according to the information provided by the source base station
via the backhaul communication unit 930. Thereby, a UE or a network
initiates a gateway reselection process according to the result of
the access control determination.
FIG. 10 is a block diagram of an MME in a communication system
according to an exemplary embodiment of the present invention.
Referring to FIG. 10, the MME includes a communication unit 1010, a
storage unit 1020, and a controller 1030.
The communication unit 1010 provides an interface for an MME to
communicate with other entities (i.e., a base station and on the
like).
The storage unit 1020 stores program codes and system information
required for the operations of the MME.
The controller 1030 controls the functions of the MME. For example,
the controller 1030 manages a control signaling of at least one
base station connected to the MME. More particularly, according to
an exemplary embodiment of the present invention, the controller
1030 controls a function for supporting gateway node reselection
for a UE. For example, the controller 1030 controls a function for
supporting gateway node reselection for a UE as illustrated in FIG.
3 to FIG. 8.
As can be seen from the above description, the above described
exemplary methods support the method of PDN GW or GGSN reselection,
depending on different mobility management processes. In the case
of user plane node reselection because the UE changes position or
is switched to another base station, the PDN GW or GGSN reselection
is implemented by optimizing the existing signaling processes. In
the case of user plane node reselection because the operator
updates the policies, the influence on the existing flows can be
reduced and the PDN GW or GGSN reselection can be implemented
rapidly.
While the invention has been shown and described with reference to
certain exemplary embodiments thereof, it will be understood by
those skilled in the art that various changes in form and details
may be made therein without departing from the spirit and scope of
the invention as defined by the appended claims and their
equivalents.
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